Torrential rains in Oklahoma; Summer in March continues for Midwest

A significant flood event is underway in Eastern Oklahoma, where widespread rainfall amounts of 3 to 5 inches have fallen since yesterday. Up to four more inches of rain is likely today, and the National Weather Service in Tulsa is warning of the potential for "widespread and potentially catastrophic areal flooding and river flooding" should some of the higher rainfall amounts being forecast materialize. Numerous main-stem rivers across eastern Oklahoma and northwest Arkansas are now approaching flood stage, and will likely experience moderate to major flooding into Wednesday. Rainfall has also been heavy over Eastern Texas, with widespread amounts of 2 - 4 inches. These heavy rains are causing some street flooding, but in general, will be a benefit, as moderate to severe drought conditions still cover most of the region.

Figure 1. Radar-estimated rainfall for Eastern Oklahoma since March 19, 2012, as estimated by the Tulsa, Oklahoma radar.

The storm system responsible is a massive, slow-moving trough of low pressure over the Western U.S. that is colliding with the warmest and moistest air mass ever recorded in March in the Central and Eastern U.S. According to the NWS in Minneapolis, Minnesota, moisture flowing northwards into Minnesota along the cold front early this week had the highest levels of moisture ever recorded so early in the year. At the boundary between the Western U.S. trough of low pressure and Central U.S. ridge of high pressure, a cold front is lifting huge quantities of moisture-laden air aloft, forcing torrential rains to fall. The cold front is also expected to trigger a Slight Risk of severe weather over East Texas, Western Louisiana, and Southern Arkansas today, says NOAA's Storm Prediction Center. Severe thunderstorm watches are already posted for much of East Texas, as seen on our Severe Weather Map. Three tornadoes were reported yesterday in Texas, and eleven touched down the previous day in Oklahoma, Nebraska, and South Dakota. The tornado that hit North Platte, Nebraska two days ago was rated a strong EF-3, and injured four people.

Figure 2. Predicted rainfall amounts for the 2-day period Tuesday morning through Thursday morning show an area of 3+ inches (orange colors) is expected over Eastern Oklahoma, Arkansas, Louisiana, and Southwest Missouri. Image credit: NOAA HPC.

Summer in March continues for the MidwestThe ongoing March heat wave in the Midwest will continue to set all-time heat records through Thursday, gradually shifting its peak intensity eastwards during the week. A few highlights from yesterday's records:

Pellston, Michigan in the Northern Lower Peninsula is called "Michigan's Icebox", since it frequently records the coldest temperatures in the state, and in the entire nation. But the past three days, Pellston has topped out at 80° - 82°F, the first 80°F March days in their history. Yesterday's 82° reading broke the previous record for the date (56° in 1976) by an amazing 26°, and was 44°F above average. Nearby Traverse City hit 83°F yesterday, the third consecutive day the city has experienced its hottest March temperature on record.

International Falls, Minnesota hit 78°F yesterday, 42° above average, and the 2nd hottest March temperature on record in the Nation's Icebox. The record of 79°F was set the previous day. Remarkably, the low temperature for International Falls bottomed out at 60°F yesterday, tying the previous record high for the date. I've never seen a station with a century-long data record have its low temperature for the date match the previous record high for the date. Yesterday was the seventh consecutive day that International Falls broke or tied a daily record. That is spectacularly hard to do for a station with a century-long weather record. The longest string of consecutive records being broken I'm aware of is nine days in a row, set June 2 - 10, 1911 in Tulsa, Oklahoma (with weather records going back to 1905.) International Falls has a good chance of surpassing nine consecutive records this week.

Record heat in CanadaRecord-breaking heat has also penetrated into the Prairie provinces of Canada over the past week. Winnipeg, Manitoba has broken its record high for the past five days in a row, and hit 24°C (75.2°F) yesterday, its hottest March temperature on record. Forecast high temperatures for Wednesday and Thursday across Ontario are near 26°C, which will threaten the records for hottest March day in history for Windsor, London, Hamilton, and Toronto.

Figure 3. The jet stream pattern features a large, southwards dipping bulge over the Western U.S., creating a trough of low pressure with cold and snow, and a large, northwards looping bulge over the Central U.S., creating a record-strength ridge of high pressure.

Why the record early-season warmth?The unusual warmth is due to a loop in the jet stream that has created a large upper-level ridge of high pressure that is stuck in place over the Eastern U.S.--a phenomenon known as a "blocking pattern." Since the jet stream acts as the boundary between cold air to the north and warm air to the south, and the large loop in the jet places its axis far to the north of the eastern U.S., summer-like warmth has developed over the eastern half of the U.S. Conversely, colder than average temperatures have developed over the western third of the U.S. behind the southwards-dipping loop of the jet stream. This jet stream pattern is too extreme to be stable, and the big loop over the Western U.S. will break off and form a giant eddy on Wednesday. The resulting area of low pressure will be known as a "cut-off low", because it will be cut off from the jet stream. The cut-off low will drift slowly eastwards during the week, gradually bringing an end to "Summer in March" over the Eastern half of the U.S.

I'm not sure if those estimates are quite accurate, lets see if we actually have rain gauges to confirm. The radar already overestimated by as must as 10 inches in parts of Texas and Oklahoma. Some areas that got the most rain(4 to 6) the radar thought they had 12-15.

However it does seem the estimates are a bit better in Louisiana, but, still, lets get rain gauges to confirm, I wouldn't trust the radar. Sometimes radar underestimates dramatically as well. It frequently underestimates here. Last years total estimated rainfall by radar over my area showed about 40-45 inches. However, actual rain gauges in my area got anywhere from 50 to 70 for last year...

I know I already talked about this last night but not everyone noticed I guess :)

Anyways, I feel its always good to find rain gauges around the area and compare them with estimates. I haven't done a careful check on Louisiana as far as rain gauges in comparison to estimates, but, I did do a few comparisons and unfortunately that stripe of 10 inches in West Louisiana is probably fairly accurate.

You have a good point Jed. Radar is not infallible and makes incorrect measurements at times. Rain gauges are the best way to measure rain if it is not to windy. I think eventually they will tweak the radar enough to get those more accurate rainfall amounts. I have witnessed the radars get it right too, so it does have the ability. In the transmitted radar signal, the electric field is perpendicular to the direction of propagation, and this direction of the electric field is the polarization of the wave. Radars use horizontal, vertical, linear and circular polarization to detect different types of reflections. For example, circular polarization is used to minimize the interference caused by rain. Linear polarization returns usually indicate metal surfaces. Random polarization returns usually indicate a fractal surface, such as rocks or soil, and are used by navigation radars. We have come a long way tho.This is Hurricane Abby approaching the coast of British Honduras. The complete eyewall cloud is visible. Location: Near British Honduras (Belize)Date 15 July 1960Source NOAA photo libAuthor NOAA's National Weather Service..Wiki

Quoting hydrus: That is a huge amount of rain in a short amount of time. I would be surprised if they dont have significant damage in some areas. Thank you for noticing my 10,000th post. It really is a milestone for me..:)..This model forecast show the precipitation levels really well..Link

I'm not sure if those estimates are quite accurate, lets see if we actually have rain gauges to confirm. The radar already overestimated by as must as 10 inches in parts of Texas and Oklahoma. Some areas that got the most rain(4 to 6) the radar thought they had 12-15.

However it does seem the estimates are a bit better in Louisiana, but, still, lets get rain gauges to confirm, I wouldn't trust the radar. Sometimes radar underestimates dramatically as well. It frequently underestimates here. Last years total estimated rainfall by radar over my area showed about 40-45 inches. However, actual rain gauges in my area got anywhere from 50 to 70 for last year...

I know I already talked about this last night but not everyone noticed I guess :)

Anyways, I feel its always good to find rain gauges around the area and compare them with estimates. I haven't done a careful check on Louisiana as far as rain gauges in comparison to estimates, but, I did do a few comparisons and unfortunately that stripe of 10 inches in West Louisiana is probably fairly accurate.

Quoting AussieStorm:Congratulations St Marys Primary School in Rydalmere, NSW, Australia(My kids school). The Weather Channel will be visiting your school on March 22.

On March 22 (the day before World Meteorological Day), The Weather Channel and Dick Whitaker will visit my kids school to:- Assist your class in making the entered weather project- Conduct a mini weather presentation- Release a weather balloon from your school grounds (whole school can get involved).

Quoting AussieStorm:Congratulations St Mary%u2019s Primary School in Rydalmere, NSW, Australia(My kids school). The Weather Channel will be visiting your school on March 22.

On March 22 (the day before World Meteorological Day), The Weather Channel and Dick Whitaker will visit my kids school to:- Assist your class in making the entered weather project- Conduct a mini weather presentation- Release a weather balloon from your school grounds (whole school can get involved).

How cool is that.

pretty cool...i just wish the NWS was doing it instead of twc. I sure woldnt be excited if TWC came to my house(IMO, of course)

Congratulations St Marys Primary School in Rydalmere, NSW, Australia(My kids school). The Weather Channel will be visiting your school on March 22.

On March 22 (the day before World Meteorological Day), The Weather Channel and Dick Whitaker will visit my kids school to:- Assist your class in making the entered weather project- Conduct a mini weather presentation- Release a weather balloon from your school grounds (whole school can get involved).

Quoting bohonkweatherman:How is Louisiana surviving? Area of La. had 15 inches on March 13 in 5 hours and received way too much rain last night. Seeing totals of over 10 inches last night in parts of La and it is still pouring.

Parts of us are under water. My town has too many road closures to name, including the main one in and out of town. The lake less than a mile from me is way up, but they opened the dam just before it all started, so it's up over the docks, but I haven't heard of it being in any houses, but not much news is out yet as to how much damage there is here. There are still cars floating I've heard in many places.

Sounding discussion... no problems with this mornings flight. Strong surface winds around 20kts from the southeast were observed at release. The winds increase nearly 30kts in the first 1500 feet of the flight. The precipitable water value was at 1.32 inches. The sounding is saturated from just below 950mb through 925mb. Dry air is located just above 750mb. The lifted index of -4.5 indicates an unstable atmosphere. Mean low level winds from the surface through 5k feet are from the southeast just under 40kts. From 5k to 10k feet the winds veer from the south and are at 37kts. The winds remain just out of the south through just below 16k feet.

&&

Previous discussion... /issued 514 am CDT Wednesday Mar 21 2012/

Short term... forecast is still on track from previous package. Latest water vapor image shows the upper level low centered near the Texas/Oklahoma border. Rain and thunderstorms are lined up across western Louisiana and are slowly making their way towards our forecast area. Some areas to the west have received well over 6 inches over the last 12 hours. As the front slowly moves our way deep moisture convergence will continue to provide the juice needed to keep the heavy rain going. Precipitable water values are expected to be in the 1.5 to 1.8 inch range during the height of the event over our area. Heavy rain and flooding will be an issue due to the slow movement of the storms and storms traversing the same areas. Expect 2 to 4 inches of rainfall for the area through Thursday evening with some locally higher amounts up to 6 inches mixed in. A Flash Flood Watch is in effect today for this reason. Right now the heaviest rainfall totals are still expected to be along and west of the Interstate 55 corridor. The possibility of some strong to severe storms is still out there as well. There is a slight risk for severe weather today with the main threats being strong gusty winds and even a possible brief spin up tornado. Cape values are expected to be near 1000 j/kg along with more than sufficient 0-1 km helicity values to get storms to rotate. A Tornado Watch is in effect this morning across the western portions of the County Warning Area until noon. The this will have to be watched as storms push through the area. Expect rain and thunderstorms to continue through Thursday as the boundary slowly moves through the area. 13/mh

How is Louisiana surviving? Area of La. had 15 inches on March 13 in 5 hours and received way too much rain last night. Seeing totals of over 10 inches last night in parts of La and it is still pouring.

Quoting aislinnpaps:Morning, Patrap. Looks like this storm is heading your way now. I hope it keeps on the move and no more stalling. We're forecasted for more rain today, but not the deluge we had. I'm going to enjoy the day off of teaching. I just got a call and one of my son's friends is now coming to stay here with his 120 pound German Shepherd. His house is going under water. The question is if he will be able to get here. Off to the kennel to find my huge crate I'm not currently using...

Be safe, I hope it all moves along as well.

The timing will be critical as Storms are beginning to fire ahead of the main Line and that's usually a bad sign. Long way to go to Max heating later.

Morning, Patrap. Looks like this storm is heading your way now. I hope it keeps on the move and no more stalling. We're forecasted for more rain today, but not the deluge we had. I'm going to enjoy the day off of teaching. I just got a call and one of my son's friends is now coming to stay here with his 120 pound German Shepherd. His house is going under water. The question is if he will be able to get here. Off to the kennel to find my huge crate I'm not currently using...